U.S. patent application number 15/947871 was filed with the patent office on 2018-12-20 for rotatable-member-supporting structure, transport device, charging device, and image forming apparatus.
This patent application is currently assigned to FUJI XEROX CO., LTD.. The applicant listed for this patent is FUJI XEROX CO., LTD.. Invention is credited to Takashi ANZAI, Takahito CHIBA, Yasunori FUJIMOTO, Atsushi FUNADA, Masataka KONISHI, Tsuyoshi SUNOHARA.
Application Number | 20180364616 15/947871 |
Document ID | / |
Family ID | 64656517 |
Filed Date | 2018-12-20 |
United States Patent
Application |
20180364616 |
Kind Code |
A1 |
FUNADA; Atsushi ; et
al. |
December 20, 2018 |
ROTATABLE-MEMBER-SUPPORTING STRUCTURE, TRANSPORT DEVICE, CHARGING
DEVICE, AND IMAGE FORMING APPARATUS
Abstract
A rotatable-member-supporting structure includes a first
rotatable member having a shaft portion, a bearing member by which
the shaft portion of the first rotatable member is rotatably
supported, a pressing member that presses the bearing member in one
direction, and a supporting member by which the bearing member is
supported in such a manner as to be retractably movable in the
direction in which the pressing member presses the bearing member.
A pressing force generated by the pressing member is greatest in a
portion of the bearing member that is on a downstream side in a
direction of rotation of the first rotatable member with respect to
an intersection between the bearing member and a first virtual line
extending from a center of rotation of the first rotatable member
toward the pressing member in the direction in which the supporting
member is retractably movable.
Inventors: |
FUNADA; Atsushi; (Kanagawa,
JP) ; KONISHI; Masataka; (Kanagawa, JP) ;
SUNOHARA; Tsuyoshi; (Kanagawa, JP) ; FUJIMOTO;
Yasunori; (Kanagawa, JP) ; CHIBA; Takahito;
(Kanagawa, JP) ; ANZAI; Takashi; (Kanagawa,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FUJI XEROX CO., LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
FUJI XEROX CO., LTD.
Tokyo
JP
|
Family ID: |
64656517 |
Appl. No.: |
15/947871 |
Filed: |
April 9, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B65H 5/062 20130101;
B65H 2404/1431 20130101; B65H 2404/1441 20130101; G03G 15/0233
20130101; G03G 15/0818 20130101; G03G 15/206 20130101; B65H 2801/06
20130101; B65H 29/125 20130101; B65H 2404/1526 20130101; B65H 29/14
20130101; B65H 2404/17 20130101; G03G 15/6529 20130101; B65H
2301/51256 20130101 |
International
Class: |
G03G 15/00 20060101
G03G015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 19, 2017 |
JP |
2017-119235 |
Claims
1. A rotatable-member-supporting structure comprising: a first
rotatable member having a shaft portion; a bearing member by which
the shaft portion of the first rotatable member is rotatably
supported; a pressing member that presses the bearing member in one
direction; and a supporting member by which the bearing member is
supported in such a manner as to be retractably movable in the
direction in which the pressing member presses the bearing member,
wherein a pressing force generated by the pressing member is
greatest in a portion of the bearing member that is on a downstream
side in a direction of rotation of the first rotatable member with
respect to an intersection between the bearing member and a first
virtual line extending from a center of rotation of the first
rotatable member toward the pressing member in the direction in
which the supporting member is retractably movable.
2. A rotatable-member-supporting structure comprising: a first
rotatable member having a shaft portion; a second rotatable member
having a shaft portion and that rotates by being in contact with
the first rotatable member; a bearing member by which the shaft
portion of the first rotatable member is rotatably supported; a
pressing member that presses the bearing member in a direction
toward the second rotatable member; and a supporting member by
which the bearing member is supported in such a manner as to be
retractably movable in the direction in which the pressing member
presses the bearing member, wherein a pressing force generated by
the pressing member is greatest in a portion of the bearing member
that is on a downstream side in a direction of rotation of the
first rotatable member with respect to an intersection between the
bearing member and a second virtual line connecting a center of
rotation of the first rotatable member and a center of rotation of
the second rotatable member.
3. The rotatable-member-supporting structure according to claim 1,
wherein the pressing member is in contact with the bearing member
at a position that is displaced toward the downstream side in the
direction of rotation of the first rotatable member from the
intersection between the bearing member and the first virtual
line.
4. The rotatable-member-supporting structure according to claim 2,
wherein the pressing member is in contact with the bearing member
at a position that is displaced toward the downstream side in the
direction of rotation of the first rotatable member from the
intersection between the bearing member and the second virtual
line.
5. The rotatable-member-supporting structure according to claim 3,
wherein the pressing member is in contact with the bearing member
such that the pressing member overlaps the intersection between the
bearing member and the first virtual line while a center of the
pressing member is displaced from the intersection.
6. The rotatable-member-supporting structure according to claim 4,
wherein the pressing member is in contact with the bearing member
such that the pressing member overlaps the intersection between the
bearing member and the second virtual line while a center of the
pressing member is displaced from the intersection.
7. The rotatable-member-supporting structure according to claim 1,
wherein the pressing force generated by the pressing member starts
to act on a portion of the bearing member that is on the downstream
side in the direction of rotation of the first rotatable member
with respect to the intersection between the bearing member and the
first virtual line.
8. The rotatable-member-supporting structure according to claim 2,
wherein the pressing force generated by the pressing member starts
to act on a portion of the bearing member that is on the downstream
side in the direction of rotation of the first rotatable member
with respect to the intersection between the bearing member and the
second virtual line.
9. The rotatable-member-supporting structure according to claim 7,
wherein a surface of the bearing member that is in contact with the
pressing member is shaped such that the surface is first in contact
with the pressing member at a position that is on the downstream
side in the direction of rotation of the first rotatable member
with respect to the intersection between the bearing member and the
first virtual line.
10. The rotatable-member-supporting structure according to claim 8,
wherein a surface of the bearing member that is in contact with the
pressing member is shaped such that the surface is first in contact
with the pressing member at a position that is on the downstream
side in the direction of rotation of the first rotatable member
with respect to the intersection between the bearing member and the
second virtual line.
11. The rotatable-member-supporting structure according to claim 7,
wherein an end of the pressing member that is in contact with the
bearing member is shaped such that the end is first in contact with
a surface of the bearing member at a position that is on the
downstream side in the direction of rotation of the first rotatable
member with respect to the intersection between the bearing member
and the first virtual line.
12. The rotatable-member-supporting structure according to claim 8,
wherein an end of the pressing member that is in contact with the
bearing member is shaped such that the end is first in contact with
a surface of the bearing member at a position that is on the
downstream side in the direction of rotation of the first rotatable
member with respect to the intersection between the bearing member
and the second virtual line.
13. An image forming apparatus comprising the
rotatable-member-supporting structure according to claim 1.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on and claims priority under 35
USC 119 from Japanese Patent Application No. 2017-119235 filed Jun.
19, 2017.
BACKGROUND
Technical Field
[0002] The present invention relates to a
rotatable-member-supporting structure, a transport device, a
charging device, and an image forming apparatus.
SUMMARY
[0003] According to an aspect of the invention, there is provided a
rotatable-member-supporting structure including a first rotatable
member having a shaft portion, a bearing member by which the shaft
portion of the first rotatable member is rotatably supported, a
pressing member that presses the bearing member in one direction,
and a supporting member by which the bearing member is supported in
such a manner as to be retractably movable in the direction in
which the pressing member presses the bearing member. A pressing
force generated by the pressing member is greatest in a portion of
the bearing member that is on a downstream side in a direction of
rotation of the first rotatable member with respect to an
intersection between the bearing member and a first virtual line
extending from a center of rotation of the first rotatable member
toward the pressing member in the direction in which the supporting
member is retractably movable.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] Exemplary embodiments of the present invention will be
described in detail based on the following figures, wherein:
[0005] FIG. 1 illustrates an outline configuration of an image
forming apparatus according to first and other exemplary
embodiments;
[0006] FIG. 2 is an enlargement of a part (a discharge transport
path near a fixing device) of the image forming apparatus
illustrated in FIG. 1;
[0007] FIG. 3 is a partially sectional diagram illustrating a pair
of discharge rollers (including supporting structures) provided
over the discharge transport path illustrated in FIG. 2;
[0008] FIG. 4A illustrates an outline of one of the supporting
structures that supports a follower roller included in the pair of
discharge rollers illustrated in FIG. 3;
[0009] FIG. 4B is a sectional diagram taken along line IVB-IVB
illustrated in FIG. 4A:
[0010] FIG. 5 illustrates an outline configuration and so forth of
the pair of discharge rollers illustrated in FIG. 3 that serves as
a decurling mechanism;
[0011] FIG. 6 illustrates the supporting structure according to the
first exemplary embodiment that supports the follower roller;
[0012] FIG. 7A illustrates the supporting structure illustrated in
FIGS. 6A and 6B that is in a state where a pressing force is
generated;
[0013] FIG. 7B illustrates the supporting structure illustrated in
FIG. 7A that is in a state where the follower roller is
rotated;
[0014] FIG. 8 illustrates an exemplary modification of the
supporting structure according to the first exemplary
embodiment;
[0015] FIG. 9A illustrates a configuration of a supporting
structure according to a second exemplary embodiment that supports
the follower roller and that is in a state where a pressing force
is generated;
[0016] FIG. 9B illustrates the supporting structure illustrated in
FIG. 9A that is in a state where the follower roller is
rotated;
[0017] FIG. 10A illustrates a configuration of a supporting
structure according to a third exemplary embodiment that supports
the follower roller and that is in a state where a pressing force
is generated;
[0018] FIG. 10B illustrates the supporting structure illustrated in
FIG. 10A that is in a state where the follower roller is
rotated;
[0019] FIG. 11 illustrates an exemplary modification of a bearing
member (only the outer shape of a relevant part is illustrated)
included in the supporting structure according to the second
exemplary embodiment;
[0020] FIG. 12 illustrates an exemplary modification of the
supporting structure according to the third exemplary
embodiment;
[0021] FIG. 13 illustrates a supporting structure according to a
fourth exemplary embodiment that supports a charging roller, and a
charging device including the same;
[0022] FIG. 14A illustrates the supporting structure illustrated in
FIG. 13 that is in a state where a pressing force is generated;
[0023] FIG. 14B illustrates the supporting structure illustrated in
FIG. 14A that is in a state where the charging roller is
rotated;
[0024] FIG. 15 illustrates an outline configuration of a
comparative supporting structure that supports a rotatable member
such as a follower roller;
[0025] FIG. 16A illustrates the supporting structure illustrated in
FIG. 15 that is in a state where a pressing force is generated;
and
[0026] FIG. 16B illustrates the supporting structure illustrated in
FIG. 16A that is in a state where the rotatable member is
rotated.
DETAILED DESCRIPTION
First Exemplary Embodiment
[0027] FIGS. 1 and 2 illustrate a first exemplary embodiment of the
present invention. FIG. 1 illustrates a configuration of an image
forming apparatus 1 according to the first exemplary embodiment.
FIG. 2 is an enlargement of a discharge transport path provided in
the image forming apparatus 1 illustrated in FIG. 1.
Overall Configuration of Image Forming Apparatus
[0028] The image forming apparatus 1 forms an image composed of
developer (toner) on a recording sheet 9, which is an exemplary
transport object or an exemplary recording material, in accordance
with information on the image, which includes any of characters,
photographs, figures, and so forth.
[0029] Referring to FIG. 1, the image forming apparatus 1 has a
housing 10 as a body thereof and includes thereinside an imaging
device 2 that forms a toner image from the toner as the developer
by an electrophotographic method or the like and transfers the
toner image to a recording sheet 9, a sheet feeding device 3 that
contains required recording sheets 9 and feeds the recording sheets
9 one by one to a transfer position defined in the imaging device
2, a fixing device 4 that fixes the toner image transferred to the
recording sheet 9, and so forth.
[0030] The housing 10 is formed of structural members, exterior
materials, and other miscellaneous members. The housing 10 has an
output receiving portion 11 at the top thereof. The output
receiving portion 11 receives the recording sheet 9 having an image
and discharged thereto. The output receiving portion 11 has a
receiving surface that is a tilted surface provided below a
discharge port 12 provided in the housing 10. The output receiving
portion 11 receives the recording sheet 9 that is discharged from
the discharge port 12.
[0031] The imaging device 2 includes a photoconductor drum 21 that
is rotatable in the direction of arrow A, and devices such as a
charging device 22, an exposure device 23, a developing device 24,
a transfer device 25, and a cleaning device 26 that are arranged in
that order around the photoconductor drum 21.
[0032] The charging device 22 employs a contact-charging method or
the like and charges the peripheral surface (the outer peripheral
surface serving as an image forming area) of the photoconductor
drum 21 to a required polarity and a required potential. The
exposure device 23 exposes the charged peripheral surface of the
photoconductor drum 21 to light (represented by a
two-dot-chain-line arrow) emitted therefrom in accordance with
image information (a signal) inputted to the image forming
apparatus 1 by a relevant method, thereby forming an electrostatic
latent image on the photoconductor drum 21. The developing device
24 supplies charged toner as the developer to the photoconductor
drum 21, thereby developing the electrostatic latent image on the
photoconductor drum 21 into a toner image. The transfer device 25
employs a contact-transfer method and electrostatically transfers
the toner image on the photoconductor drum 21 to a recording sheet
9. The cleaning device 26 cleans the photoconductor drum 21 by
removing unnecessary substances such as residual toner from the
peripheral surface of the photoconductor drum 21.
[0033] The sheet feeding device 3 includes a sheet container 31
that contains plural recording sheets 9 that are stacked on a
stacking plate 32 and are of a size, type, or the like required for
intended image formation, a feeding unit 33 that feeds the
recording sheets 9 one by one from the sheet container 31, and
other miscellaneous members.
[0034] The sheet container 31 is attached to the housing 10 in such
a manner as to be drawable therefrom. Depending on the mode of use,
plural sheet containers 31 may be provided. The recording sheet 9
may be a recording medium such as plain paper, coated paper,
cardboard, or the like that is cut into pieces of a predetermined
size.
[0035] The fixing device 4 has a housing 40 having an inlet and an
outlet and includes thereinside a heating-purpose rotatable member
41, a pressing-purpose rotatable member 42, and so forth. The
heating-purpose rotatable member 41 and the pressing-purpose
rotatable member 42 are rotatable while being in contact with each
other.
[0036] As illustrated in FIGS. 1, 2, and others, the
heating-purpose rotatable member 41 is rotatable in the direction
of the arrow illustrated in FIG. 1 and serves as a heating-purpose
fixing member provided in the form of a roller, a belt, or the
like. The heating-purpose rotatable member 41 is heated by a
heating device 43 such that the peripheral-surface temperature
thereof is kept at a required temperature. The pressing-purpose
rotatable member 42 serves as a pressing-purpose fixing member
extending substantially in the axial direction of the
heating-purpose rotatable member 41 and provided in the form of a
roller, a belt, or the like that rotates by being in contact with
the heating-purpose rotatable member 41 with a required pressure.
In the fixing device 4, the nip between the heating-purpose
rotatable member 41 and the pressing-purpose rotatable member 42 is
defined as a fixing part FN through which the recording sheet 9
having an unfixed toner image is made to pass for a required fixing
process (heating, pressurization, and so forth).
Configuration of Transport Path
[0037] In the image forming apparatus 1, as represented by a
two-dot chain line in FIG. 1, a transport path Rt along which the
recording sheet 9 is transported is defined in the housing 10. The
transport path Rt includes a feeding transport path Rt1, a relay
transport path Rt2, a discharge transport path Rt3, and so
forth.
[0038] As illustrated in FIG. 1, the feeding transport path Rt1
connects the feeding unit 33 of the sheet feeding device 3 and the
transfer position (the position where the photoconductor drum 21
and the transfer device 25 face each other) defined in the imaging
device 2 to each other. The feeding transport path Rt1 is provided
with a pair of transport rollers 34 and plural transport-guide
members (not illustrated).
[0039] The pair of transport rollers 34 serves as a pair of
registration rollers having a function of correcting the skew of
the recording sheet 9 by transporting the recording sheet 9 without
rotating, and a function of feeding the recording sheet 9 to the
transfer position by rotating in accordance with the timing of the
above transfer process.
[0040] As illustrated in FIG. 1, the relay transport path Rt2
connects the transfer position defined in the imaging device 2 and
the fixing part FN defined in the fixing device 4. The relay
transport path Rt2 is provided with a required transport-guide
member 35.
[0041] As illustrated in FIGS. 1, 2, and others, the discharge
transport path Rt3 connects the fixing part FN defined in the
fixing device 4 and the discharge port 12. The discharge transport
path Rt3 is provided with a pair of first discharge rollers 36, a
pair of second discharge rollers 37, plural discharge-guide members
38 and 39, and so forth.
[0042] The pair of first discharge rollers 36 is provided near the
outlet of the housing 40 of the fixing device 4 and includes a
driving roller 361 that is driven to rotate and a follower roller
362 that rotates by being pressed against the driving roller 361.
The pair of second discharge rollers 37 is provided at the
discharge port 12 and includes a driving roller 371 that is driven
to rotate and a follower roller 372 that rotates by being in
contact with the driving roller 371. A structure for supporting the
pair of first discharge rollers 36 and other relevant elements will
be described separately below.
[0043] The discharge-guide member 38 includes a pair of members 38a
and 38b arranged face to face with a transport space defined
therebetween. The recording sheet 9 having undergone fixing is
guided toward the pair of first discharge rollers 36 through the
transport space. The discharge-guide member 39 includes a pair of
members 39a and 39b arranged face to face with a transport space
defined therebetween. The recording sheet 9 discharged from the
pair of first discharge rollers 36 is guided toward the pair of
second discharge rollers 37 through the transport space.
Image Forming Operation Performed by Image Forming Apparatus
[0044] The image forming apparatus 1 performs an image forming
operation described below. Herein, an image forming operation in
which an image is formed on one side of the recording sheet 9 will
be described.
[0045] First, a controller (not illustrated) provided in the image
forming apparatus 1 receives a command for an image forming
operation and activates relevant devices such as the imaging device
2 and the fixing device 4.
[0046] Accordingly, in the imaging device 2, the photoconductor
drum 21 starts to rotate, the charging device 22 charges the
peripheral surface of the photoconductor drum 21 to a predetermined
polarity and a predetermined potential (in the first exemplary
embodiment, the negative polarity), and the exposure device 23
applies light to the charged peripheral surface of the
photoconductor drum 21 in accordance with image information,
whereby an electrostatic latent image of a required pattern is
formed on the photoconductor drum 21. Then, the developing device
24 supplies toner as the developer charged to a required polarity
(in the first exemplary embodiment, the negative polarity) to the
electrostatic latent image formed on the peripheral surface of the
photoconductor drum 21, thereby developing the electrostatic latent
image into a toner image.
[0047] Subsequently, the photoconductor drum 21 further rotates and
transports the toner image to the transfer position where the
photoconductor drum 21 faces the transfer device 25. Meanwhile, the
sheet feeding device 3 is activated in accordance with the timing
of transfer, and the feeding unit 33 feeds a recording sheet 9 into
the feeding transport path Rt1 up to the transfer position in the
imaging device 2. At the transfer position in the imaging device 2,
the transfer device 25 electrostatically transfers the toner image
on the photoconductor drum 21 to one side of the recording sheet 9
transported by the pair of registration rollers 34 provided in the
feeding transport path Rt1. Furthermore, the cleaning device 26
cleans relevant parts, such as the peripheral surface of the
photoconductor drum 21 having undergone transfer, for the next
imaging process.
[0048] Subsequently, in the imaging device 2, the rotating
photoconductor drum 21 sends the recording sheet 9 having the toner
image transferred thereto into the relay transport path Rt2 and
transports the recording sheet 9 toward the fixing device 4. In the
fixing device 4, the recording sheet 9 is introduced into and made
to pass through the fixing part FN between the heating-purpose
rotatable member 41 and the pressing-purpose rotatable member 42
that are rotating. When the recording sheet 9 passes through the
fixing part FN, the toner forming the toner image on the one side
of the recording sheet 9 is melted with heat and is pressurized,
whereby the toner image is fixed on the recording sheet 9.
[0049] Lastly, the recording sheet 9 having undergone fixing is
transported along the discharge transport path Rt3 and is
discharged onto the output receiving portion 11.
[0050] When the recording sheet 9 having undergone fixing is sent
from the fixing part FN in the fixing device 4, the recording sheet
9 is guided by the discharge-guide member 38 provided on the
upstream side of the discharge transport path Rt3 and is
transported to the pair of first discharge rollers 36 that is
rotating. Then, the recording sheet 9 is nipped by the pair of
first discharge rollers 36 and receives a transport force, thereby
being guided to the discharge-guide member 39 provided on the
downstream side of the discharge transport path Rt3 and being
transported to the pair of second discharge rollers 37 that is
rotating. Then, the recording sheet 9 is nipped by the pair of
second discharge rollers 37 and receives a transport force, thereby
being discharged from the discharge port 12 of the housing 10 and
is received by the output receiving portion 11.
[0051] Thus, a monochrome image composed of toner having one color
is formed on one side of a recording sheet 9, and the image forming
operation on the one side is finished. If a command for executing
an image forming operation on plural recording sheets 9 is issued,
the above process is repeated for the required number of times.
Structure of Supporting Pair of First Discharge Rollers and
Transport Device Including the Same
[0052] The image forming apparatus 1 employs a structure
illustrated in FIGS. 3 to 6 and others for supporting the pair of
first discharge rollers 36 provided in the discharge transport path
Rt3.
[0053] As illustrated in FIG. 3 and others, the pair of first
discharge rollers 36 includes, as elements of the driving roller
361 and the follower roller 362 thereof, rotatable members 5A and
5B including respective rotating shafts 51 and 52 and respective
roller portions 53 and 54 provided around the outer peripheral
surfaces of the respective rotating shafts 51 and 52. The rotating
shafts 51 and 52 are rotatably supported by predetermined
supporting members 70 with bearing members 55 and 56 interposed
therebetween and such that the roller portions 53 and 54 are
rotatable while being in contact with each other. The supporting
members 70 are fixed at respective predetermined positions.
[0054] As illustrated in FIG. 3 and others, the pair of first
discharge rollers 36 is configured such that the driving roller 361
is rotated in a required direction by receiving a required
rotational power transmitted from a driving device 77. The driving
roller 361 and the follower roller 362 in combination serve as a
transport device 7 that transports the recording sheet 9, as an
exemplary transport object, nipped between the driving roller 361
and the follower roller 362. The rotational power is transmitted
from the driving device 77 to the driving roller 361 via a rotation
transmitting mechanism (not illustrated) including a train of gears
and so forth.
[0055] The rotating shaft 51 of the driving roller 361 as the
rotatable member 5A is rotatably supported by the bearing members
55, and the bearing members 55 are each fixedly attached to a fixed
attaching portion 71A included in a corresponding one of the
supporting members 70. The fixed attaching portion 71A has a hole
or a depression into which a portion of a corresponding one of the
bearing members 55 is fitted, and includes other elements for
fixing other portions of the bearing member 55.
[0056] That is, the driving roller 361 is rotatably supported by
the supporting members 70 but the position thereof is fixed.
[0057] On the other hand, referring to FIGS. 3 to 5 and others, the
rotating shaft 52 of the follower roller 362 as the rotatable
member 5B is rotatably supported by the bearing members 56, and the
bearing members 56 are each attached to a movable attaching portion
71B included in a corresponding one of the supporting members 70.
Hence, the bearing member 56 is movable toward and away from the
driving roller 361 by a predetermined length as represented by
arrows E1 and E2. The movable attaching portion 71B has an oblong
hole or a depression into which a portion of the bearing member 56
is movably fitted, and a holding portion and so forth by which
other portions of the bearing member 56 are movably held.
[0058] The follower roller 362 is supported such that the bearing
members 56 supporting the rotating shaft 52 thereof are pressed in
the direction E1 toward the driving roller 361 by respective
pressing members 57 provided on the respective movable attaching
portions 71B.
[0059] As described above, the follower roller 362 is rotatably
supported by (the attaching portions 71B of) the supporting members
70 while being allowed to move toward and away from the driving
roller 361, and is also supported in such a manner as to be pressed
in the direction E1 toward the driving roller 361 by the pressing
members 57 with the bearing members 56 interposed therebetween.
[0060] Referring to FIGS. 4A and 4B, each bearing member 56
includes a body 56a having a substantially rectangular side face,
and a projection 56b projecting inward from the body 56a. The
bearing member 56 has a shaft hole provided substantially in the
center of the inner side face of the projection 56b and extending
through the body 56a and the projection 56b, a stepped portion 56d
provided at the upper edge of the outer side face of the body 56a
and extending substantially horizontally, and so forth.
[0061] The attaching portion 71B of the supporting member 70 to
which the bearing member 56 is attached in such a manner as to be
movable back and forth in the directions E1 and E2 includes an
oblong holding hole 72 in which the projection 56b of the bearing
member 56 is held in such a manner as to be movable back and forth
in the directions E1 and E2, a lower holding portion 73 by which
the lower part of the body 56a of the bearing member 56 is held in
such a manner as to be movable back and forth in the directions E1
and E2, and an upper holding portion 74 by which the upper part of
the body 56a of the bearing member 56 is held in such a manner as
to be movable back and forth in the directions E1 and E2.
[0062] The lower holding portion 73 includes a lower outer guide
part 73b projecting upward. The lower outer guide part 73b guides
the lower outer face of the body 56a of the bearing member 56 from
the outer side when the bearing member 56 moves as described above.
The upper holding portion 74 includes an upper outer guide part 74b
projecting downward. The upper outer guide part 74b guides the
stepped portion 56d at the outer upper edge of the body 56a of the
bearing member 56 from the outer side when the bearing member 56
moves as described above.
[0063] The pressing member 57 only needs to be capable of
elastically pressing the bearing member 56 in the direction E1
toward the driving roller 361 and may be, for example, a
compression coil spring.
[0064] The pressing member 57 in the form of a compression coil
spring has one end thereof attached to an attaching surface 56e of
the bearing member 56. The attaching surface 56e is on a side of
the body 56a that is opposite the driving roller 361. The other
end, which is a free end, of the pressing member 57 is pressed
against a receiving portion 75 projecting from the supporting
member 70, whereby the entirety of the pressing member 57 is
compressed in such a manner as to generate a required pressing
force F. Referring to FIG. 4A, the bearing member 56 further
includes a retaining projection 56f provided on the attaching
surface 56e and fitted into a space inside the compression coil
spring from the one end of the compression coil spring. The
retaining projection 56f retains the one end of the compression
coil spring so as to prevent the displacement of the one end.
[0065] As illustrated in FIGS. 3, 4A, and 4B, the follower roller
362 (the rotatable member 5B) included in the pair of first
discharge rollers 36 is used with the driving roller 361 (the
rotatable member 5A) that rotates while being in contact with the
follower roller 362. The follower roller 362 is supported by a
supporting structure 6 including the bearing member 56 by which the
rotating shaft 52 as a shaft portion of the follower roller 362 is
rotatably supported, the pressing member 57 that presses the
bearing member 56 in the direction E1 toward the driving roller
361, and (the attaching portion 71B of) the supporting member 70 by
which the bearing member 56 is supported in such a manner as to be
movable back and forth in the direction E1 in which the pressing
member 57 presses the bearing member 56.
[0066] If the driving roller 361 (the rotatable member 5A) is
ignored, the supporting structure 6 may also be regarded as a
supporting structure including the bearing member 56 by which the
rotating shaft 52 of the follower roller 362 (the rotatable member
5B) is rotatably supported, the pressing member 57 that presses the
bearing member 56 in one direction E1, and (the attaching portion
71B of) the supporting member 70 by which the bearing member 56 is
supported in such a manner as to be movable back and forth in the
direction E1 in which the pressing member 57 presses the bearing
member 56.
[0067] The roller portion 53 of the driving roller 361 has a
single-layer or multi-layer structure. At least one of the layers
of the roller portion 53 may be an elastic layer. The roller
portion 53 of the driving roller 361 according to the first
exemplary embodiment includes an elastic layer made of silicone
rubber or the like.
[0068] The roller portion 54 of the follower roller 362 also has a
single-layer or multi-layer structure. The roller portion 54 of the
follower roller 362 according to the first exemplary embodiment
includes one layer that is made of fluororesin or the like.
[0069] The pair of first discharge rollers 36 according to the
first exemplary embodiment serves as the transport device 7 as
described above and also serves as a decurling mechanism that
straightens the recording sheet 9 that is curled by passing through
the fixing device 4.
[0070] In this respect, the driving roller 361 as one of the pair
of first discharge rollers 36 is provided as an elastic roller
member that is elastically deformable, and the follower roller 362
as the other of the two is provided as a hard roller member that is
physically harder than the driving roller 361.
[0071] Specifically, the driving roller 361 is a roller member
including the roller portion 53 thereof having a multi-layer
structure including the above elastic layer. The follower roller
362 as a hard roller member has a single-layer structure including
the roller portion 54 thereof made of fluororesin or the like, as
described above.
[0072] Referring to FIG. 5, the pair of first discharge rollers 36
is configured such that the roller portion 54 of the follower
roller 362 has a diameter D2 that is smaller than a diameter D1 of
the roller portion 53 of the driving roller 361.
[0073] In such a case, as illustrated in FIG. 2 and others, the
driving roller 361 as an elastic roller member is provided on the
same side as the pressing-purpose rotatable member 42 of the fixing
device 4 with respect to the recording sheet 9 that is transported,
and the follower roller 362 as a hard roller member is provided on
the same side as the heating-purpose rotatable member 41 of the
fixing device 4 with respect to the recording sheet 9 that is
transported.
[0074] As illustrated in FIG. 5, in the pair of first discharge
rollers 36 also serving as a decurling mechanism, a part of the
roller portion 54, having the smaller diameter D2, of the follower
roller 362 that is pressed with the pressing force F into the
driving roller 361 bites a part of the roller portion 53, having
the larger diameter D1, of the driving roller 361 supported at a
fixed position. That is, the part of the roller portion 53 is
elastically deformed into a curved shape conforming to the outer
peripheral surface of the follower roller 362. In the pair of first
discharge rollers 36, the part of the roller portion 53 that is
elastically deformed while being in contact with the roller portion
54 serves as a decurling part CN.
[0075] Hence, even if the recording sheet 9 that has received the
pressure from the pressing-purpose rotatable member 42 when passing
through the fixing part FN of the fixing device 4 is deformed in
such a manner as to curl toward the pressing-purpose rotatable
member 42 (even if the recording sheet 9 comes to have a curled
part 9c represented by a two-dot chain line in FIG. 5), the curled
part 9c of the recording sheet 9 is straightened when the recording
sheet 9 passes through the nip between the pair of first discharge
rollers 36 provided in the discharge transport path Rt3.
[0076] That is, when the recording sheet 9 having curled toward the
pressing-purpose rotatable member 42 passes through the decurling
part CN in which the driving roller 361 is elastically deformed by
being pressed by the follower roller 362, the recording sheet 9 is
temporarily curled toward a side opposite the side toward which the
curled part 9c has been curled. Consequently, the curled part 9c of
the recording sheet 9 is straightened to be flat.
Defects in Structure of Supporting Pair of First Discharge
Rollers
[0077] In general, referring to FIG. 15, the supporting structure 6
that supports the follower roller 362 included in the pair of first
discharge rollers 36 is configured such that the pressing force F
generated by the pressing member 57 is centered on an intersection
P1 between the bearing member 56 and a virtual line L2 connecting a
rotation center 02 of the follower roller 362 and a rotation center
01 of the driving roller 361 to each other. The supporting
structure 6 configured as above is denoted as a comparative
supporting structure 60.
[0078] In the supporting structure 60 configured as above, the
compression coil spring as the pressing member 57 is positioned
such that a center 57a of one end face thereof substantially
coincides with the intersection P1 between the attaching surface
56e of the bearing member 56 and the virtual line L2. Note that the
two end faces of the compression coil spring extend parallel to
each other and each have a substantially flat annular shape, unless
otherwise specified.
[0079] In the supporting structure 60 that supports the follower
roller 362 illustrated in FIG. 15 and others, when the driving
roller 361 is driven to rotate, the follower roller 362 rotates in
the direction of arrow C by following the rotation of the driving
roller 361.
[0080] In this case, referring to FIG. 16A, the bearing member 56
receives a rotational force (moment) Mr generated by a frictional
force between the bearing member 56 and the rotating shaft 52 of
the follower roller 362 and that tends to rotate the bearing member
56 in the rotating direction C, and a rotational drag (moment) Mb
generated by the pressing by the pressing member 57 in the form of
the compression coil spring and that tends to stop the rotation of
the bearing member 56.
[0081] In normal times, the rotational force Mr and the rotational
drag Mb are substantially balanced with each other (Mr.apprxeq.Mb).
Therefore, as illustrated in FIG. 16A, the bearing member 56 is
kept still without being rotated about the rotating shaft 52 inside
(a movable space enclosed by) the movable attaching portion 71B of
the supporting member 70.
[0082] However, since the frictional force or the like generated
between the bearing member 56 and the rotating shaft 52 changes, a
stick-slip phenomenon may occur. If a stick-slip phenomenon occurs
in the supporting structure 60, the rotational force Mr
changes.
[0083] For example, if the rotational force Mr becomes smaller than
the rotational drag Mb (Mr<Mb), referring to FIG. 16B, the
bearing member 56 rotates about the rotating shaft 52 in a
direction opposite to the rotating direction C of the rotating
shaft 52 (the follower roller 362) (a direction toward the upstream
side in the rotating direction C) inside (the movable space
enclosed by) the movable attaching portion 71B of the supporting
member 70. In contrast, if the rotational force Mr becomes greater
than the rotational drag Mb (Mr>Mb), the bearing member 56 that
has rotated as described above returns to the initial normal
position (illustrated in FIG. 16A) or further rotates in the
rotating direction C (a direction toward the downstream side in the
rotating direction C) of the rotating shaft 52 beyond the normal
position.
[0084] That is, when the rotational force Mr changes, the bearing
member 56 at its normal position rotates in the direction opposite
to or the same as the rotating direction C of the rotating shaft 52
inside (the movable space enclosed by) the movable attaching
portion 71B of the supporting member 70.
[0085] In particular, if the bearing member 56 rotates (is tilted)
in the direction opposite to the rotating direction C of the
rotating shaft 52, as illustrated in FIG. 16B, the pressing member
57 becomes in contact with the attaching surface 56e of the bearing
member 56 that is tilted. Hence, the pressing force F generated by
the pressing member 57 contains a component force fb acting in the
direction opposite to the rotating direction C of the rotating
shaft 52. With the generation of the component force fb, the
rotational drag Mb tends to be kept large.
[0086] Consequently, in the supporting structure 60, if the bearing
member 56 at the normal position rotates in the direction opposite
to or the same as the rotating direction C of the rotating shaft 52
and then returns to the initial normal position from the rotated
position or further rotates in the opposite direction beyond the
rotated position repeatedly, noise or vibrations may occur. The
occurrence of such noise or vibrations may hinder the pair of first
discharge rollers 36 and the transport device 7 including the same
from transporting the recording sheet 9 in a good manner without
noise and vibrations.
[0087] The rotational force Mr and the stick-slip phenomenon tend
to occur if the bearing member 56 is of a type that bears the
rotating shaft 52 while allowing the sliding and rotation of the
rotating shaft 52 thereon. Such a bearing of a sliding type is made
of, for example, synthetic resin.
Features of Supporting Structure for Supporting Pair of First
Discharge Rollers and Effects Brought Thereby
[0088] As illustrated in FIGS. 4A, 6, and 7A, the supporting
structure 6 for supporting the follower roller 362, which is one of
the pair of first discharge rollers 36 according to the first
exemplary embodiment, is configured such that the pressing force F
generated by the pressing member 57 is greatest at a point of (the
attaching surface 56e of) the bearing member 56 that is on the
downstream side in the rotating direction C of the follower roller
362 with respect to the intersection P1 between the bearing member
56 and the virtual line L2 connecting the rotation center 02 of the
follower roller 362 and the rotation center 01 of the driving
roller 361.
[0089] The supporting structure 6 is not configured such that the
pressing force F generated by the pressing member 57 is greatest at
a point of the attaching surface 56e of the bearing member 56 that
is on the upstream side in the rotating direction C of the follower
roller 362 with respect to the intersection P1, so that a
satisfactory force of pressing the follower roller 362 against the
driving roller 361 is to be provided.
[0090] More specifically, as illustrated in FIGS. 6 and 7A, in the
supporting structure 6 configured as described above, the
compression coil spring as the pressing member 57 is positioned
such that the center 57a of one end face (an end face having a
substantially flat annular shape) thereof is displaced toward the
downstream side in the rotating direction C of the follower roller
362 by a predetermined length (a displacement) a from the
intersection P1 between the attaching surface 56e of the bearing
member 56 and the virtual line L2.
[0091] Hereinafter, the supporting structure 6 configured as above
is denoted as a supporting structure 6A and is distinguished from
other supporting structures.
[0092] Referring to FIG. 7A, for example, if the driving roller 361
(the rotatable member 5A) illustrated in FIG. 2 and others is
ignored, the supporting structure 6A may also be regarded as a
supporting structure configured such that the pressing force F
generated by the pressing member 57 is greatest at a point of (the
attaching surface 56e of) the bearing member 56 that is on the
downstream side in the rotating direction C of the follower roller
362 with respect to the intersection P1 between the bearing member
56 and a virtual line L1 extending from the rotation center 02 of
the follower roller 362 toward the pressing member 57 in the
directions E1 and E2 in which the attaching portion 71B of the
supporting member 70 is movable back and forth. Such a concept of
the supporting structure 6A is limited to a case where the virtual
line L1 and the virtual line L2 coincide with each other as one
continuous line.
[0093] More specifically, the supporting structure 6A illustrated
in FIGS. 6 and 7A employs a configuration in which the compression
coil spring as the pressing member 57 is positioned such that one
end face thereof overlaps the intersection P1 between the attaching
surface 56e of the bearing member 56 and the virtual line L2 while
the center 57a of the one end face is displaced from the
intersection P1.
[0094] In the supporting structure 6A illustrated in FIG. 7A that
supports the follower roller 362, the pressing force F generated by
the pressing member 57 is greatest at a point of the attaching
surface 56e of the bearing member 56 that is on the downstream side
in the rotating direction C of the follower roller 362 with respect
to the intersection P1 between the attaching surface 56e and the
virtual line L2 (or L1).
[0095] The end face of the pressing member 57 that is in contact
with the attaching surface 56e of the bearing member 56 has a
substantially flat annular shape. Therefore, the above pressing
force F is centered on the center 57a of the end face of the
pressing member 57.
[0096] In the supporting structure 6A, the pressing force F
generated by the pressing member 57 is greatest at the point of the
attaching surface 56e of the bearing member 56 that is displaced
from the intersection P1. Therefore, regardless of whether or not
the follower roller 362 is rotated, the bearing member 56 rotates
about the rotating shaft 52, as illustrated in FIG. 7B, in the same
direction as the rotating direction C of the rotating shaft 52 (the
follower roller 362) inside (the movable space enclosed by) the
movable attaching portion 71B of the supporting member 70. That is,
the bearing member 56 as a whole is tilted. In this state, the end
face of the compression coil spring as the pressing member 57 that
is in contact with the attaching surface 56e of the bearing member
56 is tilted in such a manner as to follow the tilted attaching
surface 56e of the tilted bearing member 56.
[0097] In the supporting structure 6A, when the follower roller 362
is rotating in the rotating direction C by following the rotation
of the driving roller 361, as illustrated in FIG. 7B, not only the
rotational force Mr generated by the frictional force between the
bearing member 56 and the rotating shaft 52 of the follower roller
362 and that causes the bearing member 56 to rotate in the rotating
direction C but also a second rotational force Mc described below
is generated.
[0098] Specifically, in the supporting structure 6A, as illustrated
in FIG. 7B, the pressing member 57 is in contact with the tilted
attaching surface 56e of the bearing member 56. Therefore, the
pressing force F generated by the pressing member 57 contains a
component force fc acting in a direction similar to the rotating
direction C of the rotating shaft 52, and the component force fc
acts on the bearing member 56 as the second rotational force Mc
that causes the bearing member 56 to rotate in the rotating
direction C.
[0099] That is, in the supporting structure 6A, the bearing member
56 receives two rotational forces Mr and Mc. Therefore, the bearing
member 56 is retained at a position determined after being rotated
in the same direction as the rotating direction C of the rotating
shaft 52 (the follower roller 362) inside (the movable space
enclosed by) the movable attaching portion 71B of the supporting
member 70. Hence, the bearing member 56 that has been rotated in
the same direction as the rotating direction C tends to stand still
at that position even if the stick-slip phenomenon occurs, and the
bearing member 56 becomes less likely to rotate in the direction
opposite to the rotating direction C.
[0100] Consequently, the supporting structure 6A does not make the
repeated movement that tends to occur in the comparative supporting
structure 60 (illustrated in FIGS. 15, 16A, and 16B) in which the
bearing member 56 rotates in the direction opposite to or the same
as the rotating direction C of the rotating shaft 52 and then
returns to the initial normal position or further rotates beyond
the normal position inside the movable space enclosed by the
movable attaching portion 71B. Consequently, the occurrence of
noise and vibrations attributed to the above repeated movement is
suppressed.
[0101] Since the occurrence of noise and vibrations that may occur
in the comparative supporting structure 60 is suppressed in the
supporting structure 6A, the recording sheet 9 is transported in a
good manner without the occurrence of noise and vibrations in the
pair of first discharge rollers 36 and in the transport device 7
including the same.
[0102] If the pair of first discharge rollers 36 serving as the
transport device 7 also has a function as a decurling mechanism as
described above, not only the good transport of the recording sheet
9 without noise and vibrations but also the good decurling of the
recording sheet 9 is realized.
[0103] In the supporting structure 6A, the above effects are
produced even if the bearing member 56 is of a type that bears the
rotating shaft 52 while allowing the sliding and rotation of the
rotating shaft 52 thereon.
[0104] The supporting structure 6A according to the first exemplary
embodiment only needs to be configured such that the pressing force
F generated by the pressing member 57 is greatest at a point of the
attaching surface 56e of the bearing member 56 that is on the
downstream side in the rotating direction C of the follower roller
362 with respect to the intersection P1 between the attaching
surface 56e and the virtual line L2 (or L1). Therefore, as
illustrated in FIG. 8 for example, the compression coil spring as
the pressing member 57 may be positioned such that the entirety of
the one end face thereof that is in contact with the attaching
surface 56e of the bearing member 56 does not overlap the
intersection P1 between the attaching surface 56e and the virtual
line L2 (or L1).
[0105] If the supporting structure 6A is configured as illustrated
in FIG. 8, however, compared with the case of the supporting
structure 6A (illustrated in FIGS. 6 and 7A) in which the
compression coil spring as the pressing member 57 is positioned
such that one end face thereof overlaps the intersection P1 on the
attaching surface 56e of the bearing member 56 while the center 57a
of the one end face is displaced from the intersection P1, the
pressing force F generated by the pressing member 57 acts on a
point of the attaching surface 56e of the bearing member 56 that is
further away from the intersection P1 with the virtual line L2 (or
L1), and the rate of a component of the pressing force F that
presses the bearing member 56 and the driving roller 361 is reduced
or dispersed. In this respect, the supporting structure 6A
illustrated in FIG. 8 is inferior to the supporting structure 6A
illustrated in FIGS. 6 and 7A.
[0106] Therefore, in the supporting structure 6A, the compression
coil spring as the pressing member 57 is desirably positioned such
that one end face thereof overlaps the intersection P1 between the
attaching surface 56e of the bearing member 56 and the virtual line
L2 while the center 57a of the one end face is displaced from the
intersection P1.
Second Exemplary Embodiment
[0107] FIGS. 9A and 9B illustrate a supporting structure 6B
according to a second exemplary embodiment that supports the
follower roller 362.
[0108] The supporting structure 6B has the same configuration as
the supporting structure 6A according to the first exemplary
embodiment, except that the pressing force F generated by the
pressing member starts to act on a point of the attaching surface
56e of the bearing member 56 that is on the downstream side in the
rotating direction C of the follower roller 362 with respect to the
intersection P1 between the attaching surface 56e and the virtual
line L2 (or L1). Therefore, in FIGS. 9A and 9B, elements that are
the same as those of the supporting structure 6A are denoted by
corresponding ones of the reference numerals and characters used in
the first exemplary embodiment.
[0109] As illustrated in FIG. 9A, the supporting structure 6B
according to the second exemplary embodiment includes a bearing
member 56B having an attaching surface 56f, instead of the bearing
member 56 having the attaching surface 56e that is in contact with
the pressing member 57. The attaching surface 56f is shaped in such
a manner as to be first in contact with the pressing member 57 at a
point P2 that is on the downstream side in the rotating direction C
of the follower roller 362 with respect to the intersection P1 with
the virtual line L2 (or L1). The bearing member 56B of the
supporting structure 6B is positioned such that the intersection P1
on the attaching surface 56f thereof substantially coincides with
the center 57a of the end face of the pressing member 57 that is in
contact therewith.
[0110] As illustrated in FIG. 9A, the attaching surface 56f of the
bearing member 56B according to the second exemplary embodiment is
generally continuously tilted at a required angle such that a
downstream portion thereof in the rotating direction C of the
follower roller 362 is closer to the pressing member 57 than an
upstream portion thereof.
[0111] The tilted attaching surface 56f is obtained by tilting the
attaching surface 56e of the bearing member 56 according to the
first exemplary embodiment at the required angle with reference to
the intersection P1 between the attaching surface 56e and the
virtual line L2 (or L1).
[0112] In the supporting structure 6B that supports the follower
roller 362 illustrated in FIG. 9A, a corner 57b at the one end of
the pressing member 57 is first in contact with the attaching
surface 56f of the bearing member 56B at the point P2 that is on
the downstream side in the rotating direction C of the follower
roller 362 with respect to the intersection P1. Therefore, the
pressing force F generated by the pressing member 57 starts to act
on a point (the point P2, actually) of the attaching surface 56f of
the bearing member 56B that is on the downstream side in the
rotating direction C of the follower roller 362 with respect to the
intersection P1.
[0113] That is, in the supporting structure 6B, the attaching
surface 56f of the bearing member 56B first receives the pressing
force F from the pressing member 57 at the point P2 that is
displaced from the intersection P1. Therefore, regardless of
whether or not the follower roller 362 is rotated, the bearing
member 56B rotates about the rotating shaft 52, as illustrated in
FIG. 9B, in the same direction as the rotating direction C of the
rotating shaft 52 (the follower roller 362) inside (the movable
space enclosed by) the movable attaching portion 71B of the
supporting member 70, whereby the bearing member 56B as a whole is
tilted.
[0114] In the supporting structure 6B, when the follower roller 362
is rotated, as illustrated in FIG. 9B, not only the rotational
force Mr generated by the frictional force between the bearing
member 56B and the rotating shaft 52 of the follower roller 362 and
that causes the bearing member 56B to rotate in the rotating
direction C but also a second rotational force Md described below
is generated.
[0115] Specifically, in the supporting structure 6B, as illustrated
in FIG. 9B, the pressing member 57 is in contact with a portion of
the tilted attaching surface 56f of the bearing member 56B.
Therefore, the pressing force F generated by the pressing member 57
contains a component force fd acting in a direction similar to the
rotating direction C of the rotating shaft 52, and the component
force fd acts on the bearing member 56B as the second rotational
force Md that causes the bearing member 56B to rotate in the
rotating direction C.
[0116] That is, in the supporting structure 6B, the bearing member
56B receives two rotational forces Mr and Md. Therefore, the
bearing member 56B is retained at a position determined after being
rotated in the same direction as the rotating direction C of the
rotating shaft 52 inside (the movable space enclosed by) the
movable attaching portion 71B of the supporting member 70.
[0117] Consequently, as substantially in the same manner as the
case of the supporting structure 6A according to the first
exemplary embodiment, the supporting structure 6B does not make the
repeated movement that tends to occur in the comparative supporting
structure 60 (illustrated in FIGS. 15, 16A, and 16B) in which the
bearing member 56B rotates in the direction opposite to or the same
as the rotating direction C of the rotating shaft 52 and then
returns to the initial normal position or further rotates beyond
the normal position inside the movable space enclosed by the
movable attaching portion 71B. Consequently, the occurrence of
noise and vibrations attributed to the above repeated movement is
suppressed.
[0118] Furthermore, in the supporting structure 6B, there is no
need to displace the center 57a of the pressing member 57 from the
intersection P1, unlike the case of the pressing member 57 of the
supporting structure 6A according to the first exemplary
embodiment. Instead, the shape of an end face of the bearing member
56 that is to be in contact with the pressing member 57 is changed,
whereby the above effects are produced.
[0119] Since the occurrence of noise and vibrations that may occur
in the comparative supporting structure 60 is suppressed in the
supporting structure 6B, the recording sheet 9 is transported in a
good manner without the occurrence of noise and vibrations in the
pair of first discharge rollers 36 and in the transport device 7
including the same in substantially the same manner as in the case
of the supporting structure 6A according to the first exemplary
embodiment.
[0120] In addition, the supporting structure GB has other functions
and produces corresponding effects that are substantially the same
as those described above for the supporting structure 6A according
to the first exemplary embodiment.
[0121] The bearing member 56B of the supporting structure 6B may be
replaced with, for example, a bearing member 56C shaped as
illustrated in FIG. 11.
[0122] An attaching surface of the bearing member 56C illustrated
in FIG. 11 that is to be in contact with the pressing member 57
includes a tilted portion as the attaching surface 56f only on the
downstream side in the rotating direction C of the follower roller
362 with respect to the intersection P1 between the attaching
surface and the virtual line L2 (or L1), and a substantially
horizontal portion as the attaching surface 56e on the upstream
side in the rotating direction C. The horizontal substantially
portion is the same as the attaching surface 56e of the bearing
member 56 according to the first exemplary embodiment.
[0123] The supporting structure 6B including the bearing member 56C
has functions and produces corresponding effects that are
substantially the same as those described above.
Third Exemplary Embodiment
[0124] FIGS. 10A and 10B illustrate a supporting structure 6C
according to a third exemplary embodiment that supports the
follower roller 362.
[0125] The supporting structure 6C has the same configuration as
the supporting structure 6A or 6B according to the first or second
exemplary embodiment, except that an end of the pressing member 57
is shaped in such a manner as to be first in contact with a portion
of the attaching surface 56e of the bearing member 56 that is on
the downstream side in the rotating direction C of the follower
roller 362 with respect to the intersection P1 between the
attaching surface 56e and the virtual line L2 (or L1). Therefore,
in FIGS. 10A and 10B, elements that are the same as those of the
supporting structure 6A or 6B are denoted by corresponding ones of
the reference numerals and characters used in the first or second
exemplary embodiment.
[0126] As illustrated in FIG. 10A, the supporting structure 6C
according to the third exemplary embodiment includes, instead of
the pressing member 57, a pressing member 57B having a tilted end
face 57c to be in contact with the bearing member 56. The end face
57c is generally continuously tilted at a required angle such that
a downstream portion thereof in the rotating direction C of the
follower roller 362 is closer to the bearing member 56 than an
upstream portion thereof.
[0127] The end face 57c of the pressing member 57B forms a surface
tilted at the above required angle with reference to the center 57a
thereof (the intersection between the end face 57c and the virtual
line L2 (or L1)). The pressing member 57 having such a tilted end
face 57c may be obtained by, for example, cutting an end of a
compression coil spring to be employed as the pressing member
57B.
[0128] In the supporting structure 6C illustrated in FIG. 10A that
supports the follower roller 362, an apex 57t at the end face 57c
of the pressing member 57B is first in contact with the attaching
surface 56e of the bearing member 56 at a point P3 that is on the
downstream side in the rotating direction C of the follower roller
362 with respect to the intersection P1. Therefore, the pressing
force F generated by the pressing member 57B starts to act on a
point (the point P3, actually) of the attaching surface 56e of the
bearing member 56 that is on the downstream side in the rotating
direction C of the follower roller 362 with respect to the
intersection P1.
[0129] In the supporting structure 6C, the attaching surface 56e of
the bearing member 56 first receives the pressing force F from the
apex 57t of the pressing member 57B at the point P3 that is
displaced from the intersection P1. Therefore, regardless of
whether or not the follower roller 362 is rotated, the bearing
member 56 rotates about the rotating shaft 52, as illustrated in
FIG. 10B, in the same direction as the rotating direction C of the
rotating shaft 52 (the follower roller 362) inside (the movable
space enclosed by) the movable attaching portion 71B of the
supporting member 70, whereby the bearing member 56 as a whole is
tilted.
[0130] In the supporting structure 6C, when the follower roller 362
is rotated as illustrated in FIG. 10B, not only the rotational
force Mr generated by the frictional force between the bearing
member 56 and the rotating shaft 52 of the follower roller 362 and
that causes the bearing member 56 to rotate in the rotating
direction C but also a second rotational force Me described below
is generated.
[0131] Specifically, in the supporting structure 6C, as illustrated
in FIG. 10B, the apex 57t at the tilted end face 57c of the
pressing member 57B is in contact with a point (the point P3) of
the attaching surface 56e of the bearing member 56 that is tilted.
Therefore, the pressing force F generated by the pressing member
57B contains a component force fe acting in a direction similar to
the rotating direction C of the rotating shaft 52, and the
component force fe acts on the bearing member 56 as the second
rotational force Me that causes the bearing member 56 to rotate in
the rotating direction C.
[0132] That is, in the supporting structure 6C, the bearing member
56 receives two rotational forces Mr and Me. Therefore, the bearing
member 56 is retained at a position determined after being rotated
in the same direction as the rotating direction C of the rotating
shaft 52 within (the movable space enclosed by) the movable
attaching portion 71B of the supporting member 70.
[0133] Consequently, as substantially in the same manner as the
case of the supporting structure 6A or 6B according to the first or
second exemplary embodiment, the supporting structure 6C does not
make the repeated movement that tends to occur in the comparative
supporting structure 60 (illustrated in FIGS. 15, 16A, and 16B) in
which the bearing member 56 rotates in the direction opposite to or
the same as the rotating direction C of the rotating shaft 52 and
then returns to the initial normal position or further rotates
beyond the normal position inside the movable space enclosed by the
movable attaching portion 71B. Consequently, the occurrence of
noise and vibrations attributed to the above repeated movement is
suppressed.
[0134] Furthermore, in the supporting structure 6C, there is no
need to displace the center 57a of the pressing member 57B from the
intersection P1, unlike the case of the pressing member 57 of the
supporting structure 6A according to the first exemplary
embodiment. Instead, the shape of the end face of the pressing
member 57B that is in contact with the bearing member 56 is
changed, whereby the above effects are produced.
[0135] Since the occurrence of noise and vibrations that may occur
in the comparative supporting structure 60 is suppressed in the
supporting structure 6C, the recording sheet 9 is transported in a
good manner without the occurrence of noise and vibrations in the
pair of first discharge rollers 36 and in the transport device 7
including the same in substantially the same manner as in the case
of the supporting structure 6A according to the first exemplary
embodiment.
[0136] In addition, the supporting structure 6C has other functions
and produces corresponding effects that are substantially the same
as those described above for the supporting structure 6A according
to the first exemplary embodiment.
[0137] The pressing member 57B of the supporting structure 6C may
be replaced with, for example, a pressing member 57C shaped as
illustrated in FIG. 12.
[0138] The pressing member 57C illustrated in FIG. 12 is a pressing
member (compression coil spring) whose end face (the end face of
the spring wire) 57d to be in contact with the bearing member 56 is
processed such that a portion on the downstream side in the
rotating direction C of the follower roller 362 projects and is
closer to the bearing member 56 than a portion on the upstream
side.
[0139] The supporting structure 6C including the pressing member
57C has functions and produces corresponding effects that are
substantially the same as those described above.
[0140] In the supporting structure 6C including the pressing member
57C illustrated in FIG. 12, the apex 57t at the end face 57d
thereof (the end face of the spring wire) is first in contact with
the attaching surface 56e of the bearing member 56 at a point P4
that is on the downstream side in the rotating direction C of the
follower roller 362 with respect to the intersection P1. Therefore,
the pressing force F generated by the pressing member 57C starts to
act on a point (the point P4, actually) of the attaching surface
56e of the bearing member 56 that is on the downstream side in the
rotating direction C of the follower roller 362 with respect to the
intersection P1.
Fourth Exemplary Embodiment
[0141] FIG. 13 illustrates a supporting structure 6D according to a
fourth exemplary embodiment that supports a charging roller 220,
and the charging device 22 including the same.
[0142] The supporting structure 6D supports the charging roller 220
included in the charging device 22 of the imaging device 2 and is
an application of, for example, the supporting structure 6A
(illustrated in FIGS. 6 and 7A) according to the first exemplary
embodiment.
[0143] The charging roller 220 is a rotatable member including, for
example, a rotating shaft 221 to which a charging voltage is
supplied, and a roller portion 222 provided around the rotating
shaft 221 and having a multi-layer structure including an elastic
layer, a surface layer, and so forth. The charging roller 220
rotates by being in contact with the peripheral surface of the
photoconductor drum 21 that is driven to rotate in the direction of
arrow A, thereby charging the peripheral surface of the
photoconductor drum 21.
[0144] As illustrated in FIGS. 13 and 14A, the charging roller 220
is used together with the photoconductor drum 21 that is driven to
rotate while being in contact with the charging roller 220. The
charging roller 220 is supported by the supporting structure 6D,
which includes a bearing member 56 by which the rotating shaft 221
as a shaft portion is rotatably supported, a pressing member 57
that presses the bearing member 56 in a direction E3 toward the
photoconductor drum 21, and (an attaching portion 71B of) a
supporting member 70 by which the bearing member 56 is supported in
such a manner as to be retractably movable in the direction E3 in
which the pressing member 57 presses the bearing member 56. The
pressing member 57 presses the bearing member 56 in the direction
E3.
[0145] As substantially in the same manner as the case of the
supporting structure 6A according to the first exemplary
embodiment, the supporting structure 6D according to the fourth
exemplary embodiment is configured such that, as illustrated in
FIGS. 13 and 14A, a pressing force F generated by the pressing
member 57 is greatest at a point of (an attaching surface 56e of)
the bearing member 56 that is on the downstream side in a rotating
direction D of the charging roller 220 with respect to an
intersection P1 between the attaching surface 56e and a virtual
line L2 connecting a rotation center 04 of the charging roller 220
and a rotation center 03 of the photoconductor drum 21.
[0146] In the supporting structure 6D that supports the charging
roller 220, as illustrated in FIG. 14A, the pressing force F
generated by the pressing member 57 is greatest at the point of the
attaching surface 56e of the bearing member 56 that is on the
downstream side in the rotating direction D of the charging roller
220 with respect to the intersection P1 between the attaching
surface 56e and the virtual line L2 (or L1).
[0147] An end face of the pressing member 57 that is in contact
with the attaching surface 56e of the bearing member 56 has a
substantially flat annular shape. Therefore, the above pressing
force F is centered on the center 57a of the end face of the
pressing member 57.
[0148] In the supporting structure 6D, the attaching surface 56e of
the bearing member 56 receives the greatest pressing force F from
the pressing member 57 at a point that is displaced from the
intersection P1. Therefore, regardless of whether or not the
charging roller 220 is rotated, the bearing member 56 rotates about
the rotating shaft 221, as illustrated in FIG. 14, in the same
direction as the rotating direction D of the rotating shaft 221
(the charging roller 220) inside (the movable space enclosed by)
the movable attaching portion 71B of the supporting members 70.
That is, the bearing member 56 as a whole is tilted.
[0149] In the supporting structure 6D, when the charging roller 220
is rotated in the rotating direction D by following the rotation of
the photoconductor drum 21 as illustrated in FIG. 14B, not only the
rotational force Ms generated by the frictional force between the
bearing member 56 and the rotating shaft 221 of the charging roller
220 and that causes the bearing member 56 to rotate in the rotating
direction D but also a second rotational force Mg described below
is generated.
[0150] Specifically, in the supporting structure 6D, as illustrated
in FIG. 14B, the pressing member 57 is in contact with the tilted
attaching surface 56e of the bearing member 56. Therefore, the
pressing force F generated by the pressing member 57 contains a
component force fg acting in a direction similar to the rotating
direction D of the rotating shaft 221, and the component force fg
acts on the bearing member 56 as the second rotational force Mg
that causes the bearing member 56 to rotate in the rotating
direction D.
[0151] That is, in the supporting structure 6D, the bearing member
56 receives two rotational forces Ms and Mg. Therefore, the bearing
member 56 is retained at a position determined after being rotated
in the same direction as the rotating direction D of the rotating
shaft 221 (the charging roller 220) inside (the movable space
enclosed by) the movable attaching portion 71B of the supporting
member 70.
[0152] Consequently, the supporting structure 6D does not make the
repeated movement that tends to occur in the comparative supporting
structure 60 (illustrated in FIGS. 15, 16A, and 16B) in which the
bearing member 56 rotates in the direction opposite to or the same
as the rotating direction C of the rotating shaft 52 and then
returns to the initial normal position or further rotates beyond
the normal position. Consequently, the occurrence of noise and
vibrations attributed to the above repeated movement is
suppressed.
[0153] In the charging device 22 employing the supporting structure
6D, since the occurrence of vibrations that may occur in the
comparative supporting structure 60 is suppressed, the occurrence
of charging nonuniformity attributed to the vibrations is
suppressed. Consequently, the peripheral surface of the
photoconductor drum 21 is charged in a good manner.
[0154] In addition, the supporting structure 6D has other functions
and produces corresponding effects that are substantially the same
as those described above, even if the bearing member 56 is of a
type that bears the rotating shaft 221 while allowing the sliding
and rotation of the rotating shaft 221 thereon.
Other Exemplary Embodiments
[0155] The first to third exemplary embodiments concern the
supporting structures 6A to 6C that each support the follower
roller 362 (the rotatable member 5B) included in the pair of first
discharge rollers 36. The present invention is also applicable to
the driving roller 361 (the rotatable member 5A) included in the
pair of first discharge rollers 36.
[0156] The pair of first discharge rollers 36 may have only a
function of transporting the recording sheet 9, without the
function as the decurling mechanism.
[0157] The supporting structures 6A to 6C according to the first to
third exemplary embodiment may each be applied to a supporting
structure that supports at least one of another pair of transport
rollers (rotatable members) of a transport device that are
rotatable while being pressed against each other and are configured
to transport the recording sheet 9 by nipping the recording sheet 9
therebetween.
[0158] The application of each of the supporting structures 6A to
6C according to the first to third exemplary embodiments is not
limited to the supporting structure 6D that supports the charging
roller 220 of the charging device 22 included in the imaging device
2 described in the fourth exemplary embodiment and may be another
rotatable-member-supporting structure. Examples of another
rotatable member include a transfer roller, a fixing roller, and so
forth.
[0159] The supporting structures 6A to 6C are each also applicable
to a supporting structure that supports a pressing roller to be
pressed against a portion of an endless belt that is not supported
by a supporting roller. In such a case, the rotatable member to be
in contact with the pressing roller is the portion of the rotating
belt that is not supported by the supporting roller.
[0160] The image forming apparatus including the rotatable member
and the transport device employing any of the supporting structures
6A to 6C is not limited to an apparatus that forms a monochrome
image composed of toner having a single color as described in the
first to fourth exemplary embodiment, and may be an image forming
apparatus of another type.
[0161] Examples of the image forming apparatus of another type
include an image forming apparatus that forms a multi-color image
composed of toners having different colors, an image forming
apparatus that forms an image by ejecting ink droplets, and so
forth.
[0162] The rotatable member and the transport device employing any
of the supporting structures 6A to 6C may be a rotatable member and
a transport device included in any apparatus other than the image
forming apparatus.
[0163] The foregoing description of the exemplary embodiments of
the present invention has been provided for the purposes of
illustration and description. It is not intended to be exhaustive
or to limit the invention to the precise forms disclosed.
Obviously, many modifications and variations will be apparent to
practitioners skilled in the art. The embodiments were chosen and
described in order to best explain the principles of the invention
and its practical applications, thereby enabling others skilled in
the art to understand the invention for various embodiments and
with the various modifications as are suited to the particular use
contemplated. It is intended that the scope of the invention be
defined by the following claims and their equivalents.
* * * * *